Centrifugal refractory mold and method of preparing the same



Oct. 16 1923.

W. D. MOORE GENTRIFUGAL REFRACTORY MOLD AND METHOD 0F PREPARING THE 5ml:

Filed March 8. 1925 Vljw.

i ra

Patented Oct. 16, 1923.

UNITED STATES PATENT omer..

WILLIAM DL MOORE. OF BIRMINGHAM, ALABAMA, ASSIGNOB T0 AMERICAN CAST IRON `PIPE COMPANY, 0F BIRMINGHAM, ALABAMA, A CORPORATION 0F GEORGIA.

CENTRIFUGAL BEFRACTORY MOLD AND METHOD OF PBEPARING THE SAME.

Original application illed March 1, 1923, Serial NoA 622,082.

Divided and this application filed March 8,

1923. Serial No. 823,648.

To all whom it may concern Be it known that I, WILLIAM D. Moons, a citizen of the United States, and resident ot Birmingham, in the county of .lefl'crson and State of Alabama, have invented certain new and useful lm rovements in Centrifugal Refractory Mol s and Methods of Preparing the Same, of which the following is a specification.

This invention relates to the art of centrifugally casting hollow metal bodies such as pipe, and relates more particularl to the making of such bodies in centrifugal y operated refractory molds; and has special reference to the provision of an improved refractory mold and to the method of preparing the same, this application bein a division of my application Serial o. 622,082, filed March 1, 1923.

In the centrifugal casting of metal pipe or tubes with the use of refractory material such as sand molds, the molten metal is discharged into a flask lined with a refractory material. provided with a facing on the inner surface r thereof, one well-known process comprehending the utilization of a green, moist or unbaked sand lining, and another process including the use of a baked or drv sand lining. Of these the green sand mold process has been found to be the more eco- V nomical, due for example to the time conf modulous sumption and the cost of baking the mold in the dry sand mold method, and permits of obtaining a better casting product resulting from a, number of factors. Castings obtained from the centrifugally operated green sand molds combine the desirable properties of ordinary sand cast metal such as the superior resistance to corrosion and other actions which tend to disintegrate the metal and shorten the life of the pipe, with the high qualities of centrifugally cast pipe or tubes such as the greater density and solidity and consequent greater strength and of elastieity. Although the green sand mold process is capable of yielding a superior product, the process has heretofore not met with commercial success due to the conditions that have been met with in centriu ally casting on green sand molds, whic conditions have heretofore been regarded as unavoidable and have not been successfully solved.

Among the more prominent problems presented in the art of ccntrifugally casting on refractory molds were, for example, the hardship of preventing the cutting and washing of the sand by the action of the molten metal discharging into and flowing through the mold; the further .difficult presented especially in green sand mol s of producing a clean casting without pocket ed or honeycomb defects; the further troubles accompanying the use of facings which were not properly united or associated With the sand lining, and which were picked up by and washed and carried along with the flowing metal resulting not only in the leaving of blemishesl on the surface of the casting, but the production of a prohibitive. amount of scruff, and such further mechanical objections as the instability of the sand lining when the mold is subjected to rotation at high speeds. To obviate these and other difficulties and drawbacks and to successfully produce economically that casting product obtainable in a centrifugally o erated sand mold is a prime desideratum o my present, invention.

Among the principal objects of my present invention are more specifically the provision of a method of preparing the refractory mold so that the molten metal Will flow in the mold Without those disturbances accompanying prior methods of this kind; the provision of a refractory mold having a sand composition which obviates the mechanical drawbacks found in prior practices and which permits of obtaining clean and non-defective castings; and the further provision of a mold and a method of preparing the same with a facing so as to produce a membraneous or shell-like coating performing such functions'as conditioning the surface of the sand to aid in withstanding the cutting action of the metal, in making the mold walls smooth and impervious to the flowing iron, of resisting the Washing effect of the iron, and of being of a nature as to fuse to the skin of the casting to supply the same with a protective surface coating.

To the accomplishment of the foregoing and such other objects as may hereinafter appear, my invention consists in the elements and their relation one to the other. as hereinafter particularly described and sought to be defined in the claims; reference being had to the accompanying drawings which show a preferre'cl embodiment of my invention, and in which:

Fig. 1 is a cross-sectional view of a mold showing the same with a. refractory lining and provided with a facing on the inner surface thereof, and

Fig. 2 is a view of lthe saine showing the condition of the facing and lining after the former has taken an initial or permanent set.

As hereinbefore stated, an im ortant object of my present invention reliites to the production of a refractory mold of a character and composition to obviate the mechanieal objections found in rior practice, to permit of obtaining nonefective castings andto permit the molten metal to flow over the mold surface Without setting up the disturbances hitherto encountered. As mentioned, the refractory liningr which I prefer to employ in the mold consists of a sand mixture and more particularly a green o1 unbaked sand. have discovered that the moisture content of the sand mixture plays a highly important role in the roduction of a meritorious casting, the sand) if in too dry a state having the objection of not possessing bonding power sufficient to support itself to withstand the cutting and Washing, action of the iron and the centrifugal action of the mold, and if in too moist a state giving risc to too copious a generation of steam and gas, more than the Sand is capable of taking care of, with the result that the steam is blown into the metal instead of out through the mold. making a honeycomb or pocketed casting. I have discovered that with a predetermined moisture content in the sand mixture and further with certain constituents therein. the sand is of the desired consistency and character to avoid on the one hand the mechanical difficulties including;r the washing of the Huid metal, and to obviate on the other hand the objectionable de grec of steam generation. I have further discovered that in order to properly handle iron on a green sand mold so that the metal Hows therein without material disturbance` that the manner of prepariingr the sand lining is of great importance, it being highly desirable that the mold lining be made of uniform density.

To produce the mold having the desired characteristics. I first preferably produce a sand mixture having the composition hereinbelow referred to, and sand mixture possessing a moisture content of from 7% to 11% calculated on the weight of the dry sand, and the mold or fiask is lined with the sand and rammed by means of a jolt rammel'.

For the sand lining I preferably employ a mixture of silica sand, molding sand and sharp sand containingr from 7% to 11% moisture calculated as heretofore noted on the weight of the dry sand. I have found the following mixture to give very desirable results:

Pe4 cent. Silica sand 5U Sharp sand.l 35 Molding sand 15 The rational analysis of this sand is found to be as follows:

Per cent. Quartz 80 to 85 Clay 5 to l() Feldspar 5 to 1() Uncombined water 7 to 11 This mixture I have found to possess the desired bonding power to resist washing action and to withstand any tendency to break down due to the rotation of the mold at high s eeds, and to possess a water content insu icient to cause that generation of steam and gas which has been found disadvantageous in prior practice.

In order to properly handle iron on a green sand mold, I have found it to be ot' great importance that tli'e mold be rammed 'of uniform density, and I have found that this ma be most nearly accomplished by the use o a jolt ramming process which may be operated either with air oi' electricity. To these ends the mold is placed on a jolt raminer in a vertical position. the

atterri inserted and the sand introduced into the mold, the ramming operation proceeding either after the mold is filled with the Sand or while the sand is being' introduced, the rammingr continuinplr until the sand hasbeen packed to the desired density. Although the density need not be uniform from one end of the mold to the other` since this may change from high or extra density at the lower end of the niold to a low density at the upper end ofthe saine, the density Varies uniformly from the bottoni to thc top of the mold, and it has been found that no alternate hard and soft spots or areas are produced. as is the case with other, such as the hand ramming or pneumatic rammngr methods, these alternate. hard and soft spots having been found to produce blowing and scabbing of the mold surfaces and consequently a defective casting when the metal is discharged into the mold.

Referring now to Fig. 1 of the drawings` I show diagrammatically a mold provided with a sand lining after the ramming operation, the said mold comprising a flask 10 provided With a plurality of perforations 11 distributed over the body thereof, these perforations defining vent holes for the gases and steam generated during the casting` step. and this mold may be provided with the bell end 12 Where pipe having a bell mouth end y mentioned another prime object o is desired to be produced. The inner wall of the mold is provided with the sand lining 13 having a uniform, or more correctly a uniformly varying density produced by the jolt ramming operation.

The provision of a facing for the refractory lining which satisfactorily withstands the tendency to cutting action when the metal is oured and which is so associated with the ining as to aid in preventing the breaking and cuttin of the same by the molten metal is of t e utmost importance', especially in a centrifugally operated refractory mold, and forms as already briefly my 1nven'tion.V

In the prior art numerous facings for ordinary sand molds to permit the clean cleaving of the castings from the sand and the obtaining of castings of the desired hue have been suggested and used, the facin s including powdered, liquid or plastic su stances such as plumbago carbon, cla etc., applied to 'the inner surface of the ining. The use of an appropriate facing has not, however, as far as I am aware, been hitherto suggested or em loyed in centrifugal casting methods. y my present invention I propose to employ a facing material which is applied to the surface of the moist sand mold in a powdered state, the powdered material having the properties of absorbing moisture from the sand lining, of taking a quick initial set to produce a tough membraneous or skin-like mold facing which is highl refractory, of having a low capacity for absorption cf heat and of producing a mold wall impervious to the molten metal. I have discovered that such a facing is produced with the use of natural cement, which is a pulverized product resulting from the calcination of an argillaceous limestone at a temperature only suiicient to drive ofl' the carbon dioxide.

The powdered natural cement may be applied to the face of the green sand mold by means of an apparatus such as that disclosed and claimed in my copending application ser. No. 587,999 filed Sept. 13, 1922, for a mold facing device, the application of the powdered cement being shown in Fig'. l as a powdered coating 14, this being its condition at the moment it is applied.

Immediately the application is made, however, the powdered cement begins to absorb moisture from the moist sand lining, and chemically reacts to quickly take an initial set, producing instead of a soft owdered facing a rather membraneous or s elllike facing which has a high resistance to the cutting action of the iron, this being indicated in Fig. 2 of the drawing, in which 14' represents the skin-like facing produced. Highly advantageous properties of my cement facing are the quick set that takes place pull away from the surface of the sand, exy" pands on setting, with the result that the facing tends to pack itself or imbed itself into the sand mo d proper and in the grains of the sand on the face of the mold so as to become practically an integral part thereof, the effect including conditioning of the sand lining for the high resistance to the cutting tendency when the metal is poured into the mold. Another advantageous feature of the facing is its neutral or basic character so that no chemical reaction is set up between the iron oxide on the surface and the material of which the facing is composed, this resulting in the obtaining of the very desirable separation or cleaving of the facing together With the castings from the sand and producing a casting with a smooth and permanent coating.

While in most instances I may employ natural cement in its natural state, in some instances it is desirable to mix with the natural cement a small percentage, say from to 10% of an unctuous material such as graphite or talc, the purpose of this being to act as a lubricant to aid in the s reading of the cement on the face of the molii Also in some instances where a comparatively thick facing body or wall is desired to be produced, I may impregnate the exposed surface of the cement facing with moisture as by means of a spray or atomizer, causing, the cement facing to take a quick initial set throughout the wall or body thereof. The application of moisture to the inner or exposed surface of the cement facing is conventionally illustrated in Fig. 1 of the drawing, wherein 15 indicates a spraying device or atomizer which may be moved longitudinally of the mold to apply steam or atomized moisture to the facing surface.

The facing produced on the sand lining while of a tough membraneous character also possesses the property of being fused by the heat of the molten metal after the later has distributed itself in the mold, the fusion of the cement to the metal causing the casting or pipe to retain a large portion of the same on the finished casting as a protective coating, this cement-faced casting and method of making the same being described and claimed in my application Serial No. 623,649, filed of even date herewith. It is well known that cement inhibits corrosion in all iron products, and I have empirically demonstrated that the fused cement coating on the outer surface of the casting materially (ontributes to its power of resistance to corrosion. It may be noted that because of the highly non-conducting character of the cement facing on the sand lining, the sand is liti lll]

prevented from attaining sufficient tempel'- ainre during a casting operation to fuse with the cement so that the cement coated pipe easily cleaves from the sand. Although I prefer to employ the moist sand lining mixture above described with the natural cement facing. it will be understood that other sand liningmixtures may he used to yield satisfactory results.

The practice ol' my method` the preparation of the mold and the character of the mold product will in the main be fully understood from the above detailed description thereof. Besides facilitating the casting process` and producingr an ctlicient mold and a highly meritorious product'. I have found that with my method a cheap lnetal mixture may be cmloyed. such for example as a metal mixture having the elements phosphorus. carbon` silicon. manganese and sulphur, redir ed to as low as 5% total. and the costlyl silicon content reduced from about 1y?? down to {nf/1, this beingI materially lower than the costly silicon content employed in mixtures with other processes. lt will therefore be seen that the practice of my method is generally characterized by the ease of practicing the same. the etlicient apparatus produced, the desired casting product` and the inexpensive metal mixture. used.

While l have disclosed the preferred form of my invention. it will be apparent that numerous changes may be made therein without departing from the spirit of the invention. delined in the following claims.

l claim: t

t. method oll preparing a refractory mold for use in centrifugal casting which consists in providing a hollow flask with a refractory unbaked lining and in coating the same with a powdered material having the properties of absorbingl moisture from the liningl and of .setting to form a inemhraneons or skin-like facing capable of withstanding the cutting action of the molten metal delivered in to the mold.

L?. method of preparing a refractory motd which consists in providing a flask with a refractory unbaked lining and in coating the saine with a p'owdered material having the properties of absorbing moisture from the lining and of takingl a quick initial set to form a meinbraneons or skin-like fusible facing.

It. method of preparingl a refractory mold which consists in providing a flask with a refractory unbaked lining and in coating the same with a powdered material having the properties of absorbing moisture from the lining and of expanding while setting to form a membraneous or skin-like fac- A method of preparing a refractory mold which consists in providing a. flask with a refractory unbaked lining and in coating the same. with a powdered material having the properties of absorbing moisture from the lining and expanding while setting to form a inembraneous or skin-like and fusible facing.

5. A method of preparing a refractory mold which consists in providing a flask with a refractory lining having a moisture content not less than 7%, and in coating the Same with a powdered material having the properties of absorbing moisture from the lining and of taking a quick initial set to form a membraneous or skin-like facing.

G. The method of preparing a refractory mold which consists in providing a flask with a refractory lining having a moisture content not greater than 11%. and in coating the same with a powdered material having the properties of absorbing moisture from the lining and of setting to form a membraneous or skin-like facing.

7. The methol of preparing a refractory mold which consists in providing a llas( with a refractory lining having a moisture content of from 7% to 11%, and in coating the same with a powdered material having the properties of absorbing moisture from the lining and quickly setting to form a mcmbrancous or skin-like facing.

8. The method of preparing a refractory mold which consists in providing a flask with a refractory lining having a'moisture content of from 7% to 11%, and in coating the same with a powdered material having the roperties of absorbing moisture from the ining and of setting to form a membrane'ous or skin-like facing.

9. The method of preparing a: green sand mold for use in centrifufal casting which consists in providing a iiollow flask with a green sand lining and in coating the samc with a powdered material to form a Incinbraueous or skin-like facing capable of withstanding the cutting action of the molten metal delivered into the mold.

10. The method of preparing a green san-d mold which consists in providing a flask with a green sand lining having a moisture content of from 7 to 11%. and in coating the same` with a powdered material having the properties of absorbing moisture from the lining and of taking a quick initial set to form a membraneous or skin-like facing.

11. A method of preparing a refractorv mold for use in centrifugal casting Whici consists in providing a hollow flask with a refractory unbaked lining and in coating the same with a powdered cement which absorbs moisture from the lining and sets to produce a skin-like mold facing capable of withstanding the cutting action of the molten metal delivered into the mold.

12. A method of preparing a green sand mold which consists in ro'ilig, a flask with a green `sand lining vaviii"fa. moisture content of from 7% to 11%,-*1an` jin coating the same with a powdered` V cement whic i absorbs moisture from thev linifngand sets to produce a skin-like mold facing;

13. The method of preparigarefractory mold which consists in providing a iiask4 Vwith a refractory unbaked .liningl and in the same with natural sementi?,

4'cbatfiilg the samel with a pow coating the same with cement. s

14. The method of preparing a green sand mold' which consists in 'providing a flask with a green sand lining and in coating the same with powdered natural cement.

15. A method' of preparing` a refractory mold which consists in providing a flask with a refractory unbaked lining and in coatinglthe same with a substance having the property of ex ending whileV settin to form a skin-like m0 d facingl which'pac or imbeds itself into the mold. n

16. A method of preparing a refractory mold which consists in providing a flask with a refractory unbaked ining and in coating the same with a cementitious substance having the propertycof cir-'pending while setting to form a skin-like mold facing which acks or imbeds itself into" the mold.

I7. Vmethod of preparing a refractory mold which consists in providingA a flas with a refractory unbakedfliingand 'in coatin the same with natural "nient,`

18. method of preparingga-greensand mold which consists inproviding'a ask .with a green sand lining. :tllr'ldflncoating powdered natural 19. The method of preparing mold which consists in, "pro with a refractory unbaked`, li l" coating the same with-a p j y of a cement and. a lubricant. l'

20. Themethod of preparingal mold which consists inprovidingfafias with a refractory unbakedlininf and? in coating the same with alpo-wdereiniiture of natural'cement and an unctuoii material. 21. The method of preparing l-arefraetory d which consists inipro 'di 'a 'flask lli-a refractory unbaked andi in l-inxtnre of natural cement and an'unctnous material ,l ..tQ954-%"Y0f 10% to 5% oftlie-y'unctuous material.'

a 'e lining l provided 'with askin or shell-like in the surface ofthe' moldand composed of a substance whichliuponsetting or solidifying absorbed moisture fromthe surface o the lining.

`23.".1-'A mold having a refractorylining ed with a skinor shell-like f facin :ded 'in the surface of the moldran "co osed o f a cementitious substance which upon setting or solidifying absorbed mois tent of not less than 7% and surfaced with a skin or shell-like facing imbedded in the lining surface and composed of a substance which upon setting or solidifying absorbed moisture from the surface'of the lining.

27. A mold provided with an unbaked refractory lining having a moisture content of from 7% to 11% and surfaced with a skin or shell-like facing imbedded in the face of the lining and composed of a substance which upon setting or solidifyin absorbed moisture from the surface of the inin 28. A mold havin a refractory lining provided with a fusb e skin-like facing imbedded in the face of the mold and composed of a substance which upon settin or solidifying absorbed moisture from t e surface y of the lining.

29. A green sand mold provided with ay i facing composed of natural cement.

30. A green sand mold provided with a.

facing composed of a cementitious substance expanded on to the surface of the mold.

31. A green sand cylindrical mold provided on its inner surface with a facing composed of natural cement. f

32. A refractory mold provided with a facing composed of a mixture of a cement and a lubricant.

33. A green `sand mold provided with a facing composed of a mixture of natural cement and an unctuous material such as talc or graphite.

34. The method of preparing a moist refractory mold for use in centrifu l casting which consists in providing "a ho low flask, in introducing a moist sharp sand mixture therein, 'and in ramming th-same to roduce a sand lining having uniform densities therein.

35. The method of preparing a moist refractory mold which consists in vproviding a lflask, in introducing a sand'mixture therein having a moisture content of from 7 to 11%, and in rammin the same b means of a jolt rammer to produce a sand ining having uniform densities therein.

36. The method of preparing a moist refractory mold which conslsts in providing a ask, in introducin a sandmixture therein having a composition of 50% silic'a sand,

35% sharp sand, and 15% molding sand,

and having a moisture content of from 7% to 11% calculated on the weight of the dry sand mixture, and in ramming the same by means of a jolt rammer.

37. The method of pre aring a moist refractory mold which cons1sts in providing a flask, in introducing a moist sand mixture therein, in ramming the same by means of a jolt rammer to produce a sand lining having uniform densities therein, and in coating the lining with a material which absorbs moisture from the lining and sets to form a tough membraneous facmg.

38. The method of preparing a moist refractory mold which consists in providing a flask, in introducing a sand mixture therein having a moisture content of from 7% to 11%, in ramlning the same lo'"| `i6ducc a sand lining having uniform densities therein, and in coating the lining with a material which absorbs moisture from the lining and sets to form a tough membraneous facing.

39. The method of pre 4 aring a moist refractory mold which consists in providing a flaskl in introducing a moist sand mixture therein1 in ramming the saine to produce a sand lining having uniform densities therein, and in coating the lining with a cementitious material which on setting expands and imbeds itself in the Sand lining.

40. The method of preparing apmoist refractory mold which consists in providing a flask, in introducing a sand mixture therein having a moisture content of from 7% to 11%, in ramming the same to produce a sand lining having uniform densities therein, and in coating the lining with a cementitious material which on setting expands and imbeds itself in the sand lining.

41. The method of preparing a moist refractory mold which consists in providing a flask, in introducing a moist sand mixture therein. in ramming the same to produce a sand lining having uniform densities therein, and in coating the lining with a powdered natural cement.

42. The method of preparing a moist refractory mold which consists in providing a flask` in introducing a sand mixture therein having a moisture content of from 7% to 11%, in ramming the same to produce a sand lining having uniform densities therein, and in coating the lining with a powdered natural cement.

43. The method of preparing a centrifugal refractory mold which consists in providing a hollow flask with a refractoryr unba-ked lining, and in coating the same with a cementitious material capable of withstanding the cutting actionof the molten metal delivered into the mold.

44. The method of preparing a centrifugal refractory mold which consists inproviding ahollow flask with a refractory'unbaked lining, and in coating the same with a cementitious material having the propertics of absorbing moisture from. the lining and of setting to form a membrancous or skin-like facing capable of withstanding the cutting action of the molten metal delivered into lthe mold.

45. A sand mold provided with a facing composed of a. product resulting from the calcination of an argillaceous limestone.

46. A sand mold provided with a facing facing, whereby the facing is moistened throughout t-he body thereof to cause thc same to take a set throughout.

48. A method of preparing a refractory mold which consists in providing a flask with a moist green sand lining, in coating the same with a powdered facing of cementitious material havingr the property of absorbing moisture from the lining, and in applying moisture on the inner or exposed surface of the facing, whereby the facing is moistened throughout the body thereof to cause the same to take a set throughout.

49. A method of preparing a refractory mold which consists in providing a flask with a refracto unbaked lining, in coatinfr the same wit 1 a powdered facing materiail having the property of absorbing moisture from the lining, and in applying atomized moisture on the inner or exposed surface of the facing, whereby the facing is moistened throughout the body thereof to cause the same to take a set throughout.

50. The method of preparing a moist refractory mold which consists in providing a flask, in introducing a sand mixture therein having a moisture content of from 7% to 11%, and in ramming the same to produce a sand lining having uniform densities therein. Y

51. The method of preparing a refractory mold for use in centrifugal casting which consists in lining a flask with a uniformly and densely compacted moist sand mixture having a substantial proportion of sharp and silica sand therein, and in facing the said lining with a material capable of withstanding the cutting action of the metal.

52. The method of preparing a refractory mold for use in centrifugal casting which consists in lining a flask with a uniformly and densely compacted moist sand mixture having a substantial proportion of sha-rp and silica sand therein, and in coating the said lining with a material which absorbs moisture from the lining and sets to facing united to the sand lining, said facing form a skin-likefacng. being capable of withstanding the cutting 53. A refractory mold for use in centrifuaction of the metal. 10 gal casting having a uniformly and densely Signed at New York cit in the county of 5 compacted moist sand lining made up 0f a` New York and State 0f eW York this 21st sand mixture heving a substantial proporday of February A'. D. 1923. tion of sharp and silica sand therein, and a WILLIAM D. MOORE. 

